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SEPTEMBER 2022 I PCB007 MAGAZINE 75 Fortunately for the process engineer, other factors come into play in the form of sec- ondary current distribution. e difference between primary and secondary current dis- tribution lies in understanding electrode kinet- ics in addition to solution resistance. Second- ary current distribution allows for a more uni- form current distribution across the cathode surface. is is primarily because of electrode kinetics by means of an activation overpoten- tial. is overpotential tends to make the cur- rent distribution more uniform. Compared to the primary current distri- bution, the secondary current distribution is smoother, with a smaller difference between the minimum and maximum values. When the activation overpotential is included, a high local current density would introduce a high local activation overpotential at the electrode surface, which causes the current to naturally take a different path—essentially finding its way to the lower current density areas. ere- fore, one can improve through-hole plating distribution. e engineer can improve plating distribu- tion and throwing power by manipulating the following: • Reduce cathode current density • Increase conductivity of the electrolyte— higher acid concentration • Ensure uniform solution agitation across the panels, but not excessive • Monitor contamination and organic build-up in the plating electrolyte • Increase anode-to-cathode distance— 10 inches improves throwing power vs. 6 to 8 inches Remember this is a process and needs to be controlled. PCB007 Michael Carano is VP of quality at Averatek. To read past columns, click here. At the Water's Edge: Self-assembling 2D Materials at a Liquid- Liquid Interface Molecular 2D materials find immense applica- tions in materials science, owing to their wide structural variety and easy controllability. Estab- lishing a simple and efficient method for their synthesis is, therefore, important. Now, scientists from Japan present a simple method for synthe- sizing heterolayer coordination nanosheets, a promising 2D material, shedding light on how certain chemical coordination reactions occur at liquid-liquid interfaces. Their method could help develop novel 2D materials with applications in optoelectronic devices. Coordination nanosheets are one particu- larly interesting type of 2D material. The "coor- dination" refers to the effect of metallic ions in these molecules, which act as coordination cen- ters. These centers can spontaneously create organized molecular dispositions that span mul- tiple layers in 2D materials. This has attracted the attention of materials scientists due to their favorable properties. In fact, we have only begun to scratch the surface regarding what heterolayer coordination nanosheets - coordi- nation nanosheets whose layers have different atomic composition - can offer. A team of scientists from Tokyo University of Science (TUS) and The University of Tokyo in Japan reported a remarkably simple way to syn- thesize heterolayer coordination nanosheets. Composed of the organic ligand, terpyridine, coordinating iron and cobalt, these nanosheets assemble themselves at the interface between two immiscible liquids in a peculiar way. The study, led by Prof. Hiroshi Nishihara from TUS, also included contributions from Mr. Joe Kom- eda, Dr. Kenji Takada, Dr. Hiroaki Maeda, and Dr. Naoya Fukui from TUS. (Source: Tokyo University of Science)

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